Complementary therapy should complement medical care, not substitute it. This can involve
Yoga and other relaxation and meditation techniques
Acupuncture which has been shown to improve post radiation effects in head and neck cancer, and help with nausea and neuropathy control.
Reiki therapy has been used for relaxation and symptom management.
Massage therapy has been used for management of lymphedema (or swelling related to lymph collection), and for muscle spasms and relaxation.
Alternative therapies are therapies that are pursued instead of standard medical care. This genre of therapies are commonly being lumped together as Complementary and Alternative Medicine or CAM, but they are not the same.
Around the world, in different cultures, there are other schools of medicine. e.g
Homeopathic medicine, which is practiced in India and Germany. This school of medicine delivers non-measurable amount of medicine to alter the body's way of reacting to disease.
Ayurvedic medicine is part of traditional Indian medicine, using indigenous herbal extracts
Chinese herbal medicine is extensively used as primary therapy in China
Yoga and Meditation:
It’s good for the CEO of your Insurance Company, it’s good for you. The benefits are hard to quantify and validate in clinical trials, but have been noted mostly empirically, and in small trials. More and more companies are offering yoga as an onsite benefit, or as part of your health plan.
What is Yoga?
Yoga is multi pronged approach to achieve focus of the mind. It is a spiritual, mental and physical practice that dates back several centuries, and originates in Hindu culture. It has also been adapted by Jain and Buddhist traditions, also originating in India. In the 19h century, Swami Vivekananda first introduced yoga to the Western world, and the 20th century saw yoga devotees from the Western world spread it world wide. Thus, yoga practice has moved away from its original Vedic routes, and has taken on attributes that have focused on the physical, e.g. “hot yoga”. Yoga has evolved into different schools of practice, e.g. hatha yoga, which concentrates on physical and mental strength building postures (asanas) and exercises. These are best learnt under the tutelage of a qualified yoga instructor, as doing the poses incorrectly can cause muscle injuries. Bhakti yoga is a more devotional or meditational form of yoga.
What is meditation?
Meditation is a spiritual practice that started thousands of years ago, and its origin is attributed to India. From there, it took many forms as the practice travelled through Asia, as Buddhism spread to China and Japan, and with Islamic Sufi practices. Judeo Christian meditation is more focused on prayer and contemplation, rather 
than specific chants or ritual practices.
However, in the modern era, meditation has shifted more into the realm of relaxation and self-awareness, using breathing exercises, posture training and mindfulness techniques. The practice has moved out of the religious sphere and has also been noted to have many health benefits.
There are many techniques that are recommended. Commonly, people assume a posture, and concentrate on deep breathing. Some use a word that is repeated, like a mantra, which can assist in being able to focus. Relaxation sounds like recordings of the sea can induce a state of relaxation.
Additional mindfulness techniques have been used to help patients deal with anxiety and additions, pain, and chronic illnesses.
All these practices can be modified to your own needs, and can be practiced to your own satisfaction. Yoga classes are available in most cities, and meditation apps can help get you started.